Treatment of wet ESP effluent using magnesium hydroxide slurry

Electric utilities are seeing increased pressure from regulators, environmental groups, and the public to control both air and water pollutants. The higher cost, short supply, and higher level of elemental mercury concentrations of low-sulfur coal will keep them burning high-sulfur coal. The wet electrostatic precipitator (wet ESP) has been an effective method for eliminating SO3 and acidic mists in flue gas at electric power generation plants...

Oct 6th, 2008

BALTIMORE, MD, Oct. 1, 2008 -- Electric utilities are seeing increased pressure from regulators, environmental groups, and the public to control both air and water pollutants. The higher cost, short supply, and higher level of elemental mercury concentrations of low-sulfur coal will keep them burning high-sulfur coal. The wet electrostatic precipitator (wet ESP) has been an effective method for eliminating SO3 and acidic mists in flue gas at electric power generation plants. In this process, a water mist is injected into the flue gas stream after flue gas desulfurization to capture SO3. The SO3 gas is absorbed by the water to form a sulfuric acid solution that enhances the ESP operation. This acidic effluent must be neutralized prior to discharge into surface waters or for reuse.

The addition of an alkali such as FloMag®H Magnesium Hydroxide Slurry ( Mg(OH)2 ) can effectively neutralize wet ESP effluent by providing more alkalinity per pound than other alkalis (Table 1). As shown in Table 1, less magnesium hydroxide is required on a dry basis than caustic soda, hydrated lime and soda ash to neutralize one ton of sulfuric acid. FloMag®H also generates less total dissolved solids than these other alkalis.

As shown in Figure 1, FloMag®H can be injected at the wet ESP discharge to adjust the pH within permitted discharge limits. Since FloMag®H buffers to pH 9.0, it maintains a controlled pH even with an over-addition of Mg(OH)2. Unlike hydrated lime that forms insoluble calcium sulfate solids (see Table 1), FloMag®H forms soluble salts that results in lower sludge volume. Compared to caustic soda and hydrated lime, FloMag®H is non-D.O.T. regulated, non-hazardous and non-corrosive making handling safer and easier for operators.

FloMag H benefits include:

• Greater Neutralizing Value• One gallon of FloMag replaces 1.77 gallons of 50% caustic soda. >> Click here to compare the properties of FloMag with those of other industrial alkalis• Buffering Ability• Magnesium hydroxide naturally buffers at about 9 pH, precluding pH excursions. The rate at which neutralization occurs is more controlled than other alkalis.• Environmentally Friendly / Safe• FloMag is a high purity, industrial grade Milk of Magnesia. FloMag is non-toxic, non-corrosive, non-hazardous, and safe for employees.